Results
All birds had enlarged congestive greenish-black tinged livers with a
reticulate pattern, enlarged kidneys and mottled locally pale pectoral
muscles (Figure 1A-C). The distribution, type and severity of lesions
varied between animals. In all cases, the most prominent microscopic
lesions were hyperemia and congestion, necrosis and mononuclear
inflammatory infiltrates consisting of lymphoid cells, plasma cells and
histiocytes, although to a different degree depending on the tissue. The
liver showed congested central veins, an enlarged sinusoidal area,
hemozoin pigment within hyperplastic Kupffer cells, and dense
lymphoplasmacytic and histiocytic inflammatory cells within the portal
tract and in perivascular spaces (Figure 1D). However, the most striking
finding in the liver was the great number of phanerozoites inside
hepatic cells (Figure 1D, inset). Other organs affected included the
heart and, especially, the kidney, where multifocal necrosis along with
mononuclear and polymorphonuclear infiltrates were the most important
lesions (Figure 1E). Phanerozoites were also observed in other organs,
especially in the skin and muscle where they were associated to
multifocal necrosis as well as mononuclear and polymorphonuclear
infiltrates (Figure 1F). In the spleen, lymphoid depletion, necrotic
foci of lymphoid cells, multifocal granulocytic infiltrates and a severe
hemosiderosis were evident. In the lung, oedema and congestion, as well
as moderate to severe diffuse interstitial bronchopneumonia were
observed. Lesions in the central nervous system were characterized by
oedema, congestion, gliosis, neuronal necrosis, perivascular cuffing,
capillary endothelial cell swelling, and perivascular infiltrates
composed of mononuclear cells.
Using immunohistochemistry, BAGV antigen was detected in numerous
organs, including spleen, liver, lung, kidney, central nervous system
and muscle (Figure 1G, H). Specifically, antigen was detected in the
cytoplasm of neurons and glial cells, endothelial and epithelial cells,
macrophages and hepatocytes, often associated to necrotic foci (Figure
1H). Plamodium spp. phanerozoites observed in the hematoxilin-eosin
stained tissues were confirmed to be Plasmodium spp. by
immunohistochemistry (Figure 1I).
Bagaza virus was identified by real time RT-PCR and subsequent
sequencing in vascular feather and brain samples of the partridges
(Figure 2), while all tested tissues (feather, brain, spleen, heart,
liver) also tested positive for Plasmodium spp.